1. Field of the Invention
The present invention relates to a semiconductor laser device, and more particularly, it relates to a semiconductor laser device mounted with a plurality of leads electrically isolated from each other, a heatsink and a semiconductor laser element portion.
2. Description of the Background Art
With reduction in the size and the thickness of an optical pickup, a semiconductor laser device employed as a light source has been required to be reduced in size. On the other hand, however, when the semiconductor laser device is downsized, a heatsink mounted on the semiconductor laser device is also downsized, thereby disadvantageously deteriorating heat radiability.
A semiconductor laser device suppressing reduction of heat radiability while enabling downsizing is heretofore proposed, as disclosed in Japanese Patent Laying-Open No. 2001-111152, for example.
The aforementioned Japanese Patent Laying-Open No. 2001-111152 discloses a semiconductor laser device comprising a laser chip (semiconductor laser element portion), a heatsink mounted with the laser chip and three leads electrically isolated from each other. In this semiconductor laser device, assuming that an emission direction of a laser beam is a front side, a rear end of the heatsink is arranged frontward of forward ends of the leads. The heatsink is so formed as to extend in a direction of an upper side where the laser chip is mounted. Thus, the size of the heatsink can be increased without increasing the size of the semiconductor laser device. Consequently, deterioration of heat radiability can be suppressed while enabling downsizing of the semiconductor laser device. In the semiconductor laser device disclosed in the aforementioned Japanese Patent Laying-Open No. 2001-111152, a surface of the heatsink is connected to side surfaces of the leads through wires.
In the semiconductor laser device described in the aforementioned Japanese Patent Laying-Open No. 2001-111152, however, while the reduction of the heat radiability can be suppressed to some extent while enabling downsizing, the distance between the rear end of the heatsink and a body is increased and hence the heat radiability is deteriorated. Additionally, the length of the semiconductor laser device in the emission direction of the laser beam of is increased. Further, leads and a surface portion of the heatsink arranged frontward of the leads are connected to the side surfaces of the leads through the wires and hence the length of each wire is disadvantageously longer than the shortest distance from the surface of the heatsink to each lead. Thus, inductance of the semiconductor laser device is increased as compared with a case of connection at the shortest distance, and hence high speed responsibility is disadvantageously deteriorated.